A low response has been found to be a predictor of future alcohol use disorders among various populations, including Native Americans and Koreans.19,20 However, contradictory results have been observed in other studies. These inconsistencies have been attributed to differing methods of alcohol administration and limited sample size.21-23 An estimated 40% of offspring of alcoholics have a low response to alcohol, and prospective studies have shown that it may be a predictor of future development of alcohol use disorders among alcoholic offspring.24-26 Both animal and human twin studies have found that response is genetically influenced.15 Genetic factors are estimated to account for 60% of the variance in response to alcohol.12,27 Among certain populations, low response could explain up to 50% of the relationship between family history of alcohol use disorders and risk of alcoholism.11 In a recent review, data from various animal and human studies were summarized and various candidate genes involved were implicated in influencing level of response to alcohol.15 These include genes related to the second-messenger system (adenylyl cyclase [AC]/cyclic adenosine-3′,5′-monophosphate [cAMP] system), neurotransmitters (endogenous opioids, serotonin, γ-aminobutyric acid
